Manufacture of synthetic camphor by means of a liquid catalyst



Patented Sept. 6,1927.

UNITED ,STATES LEON DARBASSE AND ETIENNE DABRASSE, on rams, AND LUCIEN DUPONT,

vmcnnnns, FRANCE.

1,641,579 PATENT OFFICE.

MANUFACTURE OF SYNTHETIC 'QAMPHOR BY MEANS OF A LIQUID CATALYST.

No Drawing. Application filed June 1, 1921-, Serial No. 474,190, and in France June 9, 1920.

The fixation of organic acids with essence of turpentine in order to obtain bornyl or isobornyl esters is known since the Work of Bouchardat and-Lafont.

This reaction has been the object of several patents having for their purpose the industrial manufacture of synthetic cam-.

phor, eachpatent corresponding to an acid or a group of acids having special properties. Among the acids the use of which has already been mentioned in previous patents,

one can mention particularly oxalic acid,-

' it is noticed that the essential feature of these processes consists in the application of heat to a mixture of oxalic acid and of name of contacting agent essence of turpentine. This mixture is generally raised to a temperature of 120- to 130 'C. One obtains in this manner turpentine and isobornyl esters of oxalic and formic acids.

The action of heat at the temperature of the reaction causes therefore a decomposition. of free or combined oxalicacid, giving bornyl formate. Moreover, owing to hydrolysis', esters and terpinolic compounds are formed at that temperature the yield being reduced thereby. This process as described in the previouspatents gives a poor yield, both as concerns the essence of turpentine, which is transformed and polymerized, and the oxalic acid, which is partly decomposed.

A second and more interesting patent is the French Patent No. 393,478 dated 19th August, 1908, to the Chemische Fabrik auf Actiengesellschaft (vorm. E. Schering). In this patent, Schering claims theuse of a catalyst to promote the reaction of oxalic acid onturpentine. He uses exclusively metallic chloridesas catalyst, under the and, among these chlorides, he particularly selects aluminium chloride; he also mentions chloride of antimony, and phosphorus and zinc chlorides. In his patent Schering states that, eventually, one can use a diluting agent such as benzol or carbon tetrachloride, but without insisting on this point. the said diluting agent being added rather to moderate the reaction, which is particularly energetic with such an active. agent as alumimumchloride since he mentions that it is necessary to moderate it by artificial cooling when the temperature reaches 70 C.

'With the present invention, while oxalic acid is used for the manufacture of bornyl ester, all the drawbacks pointed out above can be eliminated; almost the whole of the turpentine taking part in the reaction being utilized. As to the uncombined turpentine it is not altered and can be used over again either for the same purpose. or any other use to which turpentine can be puti The means by which these improvements are obtained consist in using a liquid catalyst. Among the catalysts 'ving the best results mention must be ma e of chlorinatedand brominated hydrocarbons, Iand, among these, methylene. chloride, chloroform carbon tetrachloride, ethylene chloride, ethylene bromide ,'and especially the carbons, a'ndparticularly, in this series, tetrachlorethane. Benzene and acetone, on the other hand, appear to be very inferior catalysts. These various catalysts exhibit very different properties, first as to the speed of the reaction and then as to the quality of series of the acetylenic chlorinated hydro;

the products, chloroform is more rapid than carbon, tetrachloride, but both, are

slower than the tetrachlorethane and the trichlorethylene.

otherhand the rise of temperature acoelerates the reaction to an extraordinary degree. A reaction which takes hours at 75". C.v to utilize the whole of the oxalic acid used, is com leted in 20 minutes at 140150- C. A ast reason Ofl great importance, which also favours a relatively berneol eminently adapted to the manufac-' ture of camphor. One finds again here in this case the influence of temperature, com-L parable to that of the well known action of gaseous hydrochloric acid on essence of tur entine.

he'manner in which the process is carried out consists in heating together to a 'tem erature of 115 to 120 C. the mixture of 11 uid catal st, essence of turpentine and anhy rousoxa 1c acid, (3 1-1 y For catalysts of relatively low boiling point suclras chloroform, trichlorethylene, carbon'tetrachloride, the ratio of the weight of the essence of turpentine and the catalyst mustbesuch that the ebullition of the mixture takes place at the re uired tem erature.

Even with'a ver volatile l)ody like t e tetrachloride of car on it is necessary to have a mixture containing a large proportion of the tetrachloride in order that the ebullition should begin and remain at 125 C. One will even easily attain 130-140.C.

Oxalic acid is slightly. soluble in the mixture, it dissolves gradually during the re action and entirely disap ears at the end. A small proportion of 801$ bornyl oxalate is formed approximately 2 to of the weight of the oxalic acid used, but the princan be easily recovered.

cipal body formed during the catalysis, except bornyl format'e is neutral oxalate. The two carboxylic groups of oxalic acid enter v1n combination contrarily to what takes place in the rocesses which are based on the esterificat on of turpentine with sebacic acid, and also to what takes place with the various other acids derived of the hthalic series which have. been used for t e same purpose and with which acid esters are obtamed.

I Neutral bornyl oxalate, O,,O,(C H is not decomposed at a temperature sensibly above/100 C. It is a nonvolatile body; it

i can therefore be easily separated from the turpentine in excess either by steam distillation, or by d stillation in vacuum it decomposes ata hightemperature. Bornyl oxalate is very easily saponified, even by very The prode saponification is isoborneol and dilute aqneous solutions. of soda. not of t sodium oxalate; from the latter, .oxalic acid The-catalytic action is clearly demonstrated by the difierencebetween thev times required to, complete the reaction at a temperature 1n,,t ,he vicinity of 100. For completion, the reaction requires hours with tetrachlorethane, hours with chloroform and over hours with carbon tetrachloride: at a temperature of'140, it is terminated in half an hour with tetrachlorethane. It is also clearly markedby the differences between, the products obtained. This, besides the novelty of the new catalysts used, such as the tetrachlorethane, lainly diiierentiate the process from those described in the above mentioned patents.

As mentioned above. all the acids can be used, with the help of the liquid catalysts which we mention, with a noteworthy improvement in the yield as compared with their yield without a ,catalyst.

We have tried the different organic acids:

formic, acetic, butyric, sebacic, benzoic, salicylic, etc. However. for the various reasons: cost, smallmolecular weight, ease of separation of the formic ester from turpentine, facility of saponificatiomofbornyl oxalate and'convenience of recovery of oxalic acid, we have given preference to the latter oxalic acid. y

In a similar manner, although the chlorinated compounds of acetylene. trichlorethylene. and tetrachlorethane, have a more rapid action, We prefer the ,useof carbon tetrachloride as catalyst, owing, to its lower.

cost and the greater ease with which it is separated from turpentine.

An example is given below of this improved process:

. A mixture of 40 parts of turpentine free from water, 20 parts of carbon tetrachloride free from water and 5 parts of anhydrous oxalic acid is heated by steam to ebullition with a reflux condenser. k t,

If necessary, a little "tetrachloride is first allowed to distil out in order to ,ensure that the internal temperature of the boiling liquid is 115 C. the reflux condenser is put inaction and the ebullition \is continued until the oxalic acid is completely dissolved; when the latter has entirely disappeared, which requires 7 to 8 hours, the remaining liquid is distilled first in vacuum, and subseouently with steam.

The distillate contains tetrachlorethane' and the turpentine in excess'n One can. either separate them by rectification, or ad to the mixture a proportion ofi .tu rpentine equivalent to that which has entered 'nto combination in order to begin a fre sh o er ation.

The residue of the di'stillatitin consists 1 The borneol is collected by filtration of the solution of sodium oxalate. It can be also carried off by steam distillation, it is then obtained in a cleaner state. The oxidation of this borneol by one of the known methods leads to camphor, directly, with good yields. 1

We claim:

1. In the process of makin camphor from turpentine byconverting tIie pinene into bornyl ester, saponifying the ester to produce borneol and oxidizing the borneol to camphor; the improvement which comprises acting on turpentine with oxalic acid and a liquid catalyst consisting solely of a halogenated open chain hydrocarbon at a temperature that is substantially the boiling point of the mixture.

2. In a process of making camphor from turpentine by converting the pinene into' bornyl ester, saponifying the ester to produce borneol and oxidizing the borneol to camphor; the improvement which comprises acting on turpentine with oxalic acid and a liquid catalyst consisting solely of a halogenated open chain hydrocarbon at the boiling point of the mixture, and controlling the temperature of the reaction by the quantity of turpentine present.

3. In the process of makingleamphor from turpentine by converting t e pinene into bornyl ester, sapvonifying the ester to produce borneol and oxidizing the borneol to camphor; the improvement which comprises acting on turpentine with oxalic acid in the presence of a halogenated'open-chain saturated hydrocarbon acting as a sole catalyst for the reaction between said acid and turpentine at a temperature, atwhich the mixture boils, to produce bornyl oxalate.

4. In the process of making camphor from turpent ne by converting the pinene into bornyl ester, saponifying the ester to pro' duce borneol, and oxidizing the borneol to camphor; the improvement which comprises acting on turpentine with oxalic acid in the presence solely of a liquid halogenated open chain hydrocarbon at a temperature not less than (3., to produce bornyl'oxalate.

5. In the process ofmaking camphor from turpentine by converting the pinene "into bornyl ester, saponifying the ester to produce borneol and oxidizing the borneol to camphor; the improvement which consists in acting .on turpentine with oxalic acid in the presence of tetrachlorethane at a temperature between 100 and C. to produce bornyl oxalate. v

In testimony that we claim the foregoing as our invention. we have signed our names.

LEON DARRASSE. ETIENNE DARRASSE. LUCIEN DUPONT. 

